The invention relates to aziridinosilicones and to the use thereof, in particular in dental preparations.
For the purposes of this invention, the term aziridinosilicones is taken to mean oily or resinous polymeric siloxanes which have been functionalized with aziridino groups (analogous to the term “vinyl- or hydridosilicone oils” in A. Tomanek, Silicone & Technik [Silicones & Technology], Hanser 1990, p. 37).
High-precision elastic impression materials which are distinguished by high impression accuracy, high dimensional stability and good detail reproduction are, for example, materials based on agar, polysulfides, polyethers or addition-crosslinking silicones.
In the case of the addition-crosslinking silicone impression materials, curing is achieved by reaction of a polysiloxane containing vinyl end groups with a poly-siloxane containing SiH groups using platinum catalysts. The impressions obtained in this way are distinguished by very good elastic properties and high storage stabilities. These materials have always had the disadvantage of low hydrophilicity, which results in low drawing sharpness owing to a poor flow capacity.
In order to improve the hydrophilic behavior of silicone impression materials, hydrophilizing additives are added to the addition-crosslinking silicone impression materials. However, the better wettability achieved in this way is also accompanied by increased water absorption on contact with moist media, which can result in impaired dimensional stability and increased evolution of hydrogen.
In the case of the pure polyether materials, aziridine-containing substances are polymerized, as described in U.S. Pat. Nos. 3,453,242 and 4,093,555 or in DE-A-43 06 997. The sulfonium salts disclosed in U.S. Pat. No. 4,167,618, for example, are suitable for initiating the polymerization. Polyether impression materials prepared in this way have natural hydrophilic properties.
There have been various attempts to combine the hydrophilic properties of polyethers with the good elastic properties of silicones.
DE-A-37 41 575, DE-A-40 19 249, DE-A-40 10 281 and DE-A-38 38 587 describe materials based on a platinum-catalyzed addition reaction of an Si—H component with an unsaturated polyether. In contrast to addition-crosslinking silicones, the unsaturated polyether is generally the principal constituent, which provides the matrix with a hydrophilic characteristic.
DE-A-40 19 249 describes curable materials which, besides unsaturated polyethers containing alkenyl radicals, also comprise the products of the reaction of substituted polyethers of this type with oligosiloxanes containing at least two Si—H groups in the molecule and platinum catalysts as principal constituents.
In order to achieve an adequate storage stability, it is necessary to separate the reactive constituents spatially from one another. The Si—H compound and the platinum catalyst necessary for curing at room temperature cannot be combined in a paste since the Si—H compound would decompose.
During storage over a period of from several weeks to months, however, the problem arises that the catalyst component in which the platinum catalyst is combined with the unsaturated polyether has an unsatisfactory storage stability.
However, the dentist or technician needs to have access to an impression material which has a long storage stability and is guaranteed to be usable over a period of from several months to years.
DE-A-40 10 281 therefore proposes the addition of antioxidants in order to increase the storage stability. However, even this proposal results in unsatisfactory long-term storage stability.
DE-A-197 19 438 describes addition-crosslinking polyether impression materials which are distinguished by good storage stability of the catalyst component and of the base component and also of the cured dental material. These dental materials have the disadvantage of a low level of mechanical properties, meaning that they can only be employed to a restricted extent for dental impressions.
The object of the present invention is to provide curable materials which do not have the disadvantages of the prior art.